电纺丝法制备聚乳酸/多壁碳纳米管/羟基磷灰石杂化纳米纤维的研究

电纺丝是一种利用聚合物溶液或熔体在强电场中进行喷射纺丝的加工技术,所制得的纤维、直径一般在数十纳米至几微米之间,比传统方法制得的纤维直径小几个数量级,是获得纳米尺寸长纤维的有效方法之一．     

Hydroxyapatite/polyurethane composites as promising biomaterials

The biomaterials are intended to augment or replace the function of tissues or organs in human body. Every year millions of people require soft- or hard-tissue regeneration worldwide. Polymers and their composites are a large class of biomaterials appreciated for tissue regeneration. Polyurethane (PUR) is an organic synthetic multifunctional polymer with established biomedical applications. The hydroxyapatite (HA) is one of the biocompatible ceramic materials similar to natural bone material. The amalgamation of hydroxyapatite with polyurethane enhances the bioactivity of final product along with the combination of individual properties. Here, we review the synthesis, characterization, and applications studies of HA/PUR-based biomaterials. We initiate this review with a brief and representative compilation of the chemical composition and methods of preparation for HA/PUR biomaterials. Then, moving ahead, first, we review the simple HA/PUR biomaterials and use of PUR templates. Second, we review the significance of modified HA and PUR in these biomaterials. Third, we discuss the potential of bio-based PUR and inclusion of third constituent in the HA/PUR biomaterials. Then, we appraise the involvement of trace nutrient in deposition of HA on PUR scaffolds. Finally, we consider the other expedient applications of HA/PUR composites such as drug delivery system and sorbent of pollutants.     

Water dispersible hydroxyapatite nanoparticles functionalized by a family of aminoalkyl phosphates

A series of aminoalkyl phosphates (AAP-n, with carbon number n ranging from 2 to 6) are used as surface modifiers to prepare hydroxyapatite hydrocolloids. The resulting nanoparticles (Cn-HA) possess a coreshell structure where an ionized layer of calcium-(AAP-n) complex [⁺H₃N-(CH₂)_n-OPO₃Ca] encapsulates each hydroxyapatite core. Long-term colloidal stability is achieved due to the electrostatic repulsion among the suspending particles. The incorporation of AAP-n results in a preferential crystal growth along c-axis, showing an increasing aspect ratio of particles from C2-HA to C6-HA. Preliminary cell culture using osteoblast-like MG63 cells shows no cytotoxicity associated with the as-prepared Cn-HA particles. The functional amino groups around the nanoparticles could be used to graft various organic chains to prepare homogeneous HA/polymer composites as bone grafting materials.     

Zn and Ag Doping on Hydroxyapatite: Influence on the Adhesion Strength of High-Molecular Polymer Polycaprolactone

In this study, density functional theory was employed to calculate the adsorption of polycaprolactone (PCL) by pure hydroxyapatite (HA), Zn-doped HA, and Ag-doped HA, and the interaction of PCL on the surface of HA (001) was simulated. The results show that there was significant electron transfer between the carbonyl O in PCL and the Zn, Ag, and Ca in HA, forming coordinate bonds. The binding energies of Ag-doped HA/PCL and Zn-doped HA/PCL were much higher than those of HA/PCL. HA doped with Ag had the highest binding energy to PCL. Therefore, we believe that when HA is doped with Ag atoms, its adsorption capacity for PCL can be increased. The results obtained in this study can be used as a guide for the development of HA/PCL bone graft composite material doped with appropriate metal ions to improve its adsorption capacity.     

生物降解高分子/羟基磷灰石复合材料研究进展

由于高分子/HA复合材料兼具HA优良的生物性能和高分子材料良好的力学性能而受到了广泛的重视.本文综述了近年来生物降解高分子/羟基磷灰石复合材料的研究进展,介绍了胶原及其衍生物、聚酯、甲壳素及其衍生物、淀粉等可降解高分子材料与羟基磷灰石复合作为骨修复材料的研究进展,并对此类材料存在的问题和发展前景进行了讨论.     

Characterization of hdpe/ha Composites Treated with Titanate and Zirconate Coupling Agents

The development of new materials for bone substitution has been of great interest for the scientific community in the last years. High-density polyethylene (HDPE) and hydroxyapatite (HA) composites have been used in biomedical applications without any inflammatory response. However, the differences in nature of both materials have motivated the use of coupling agents to improve their interfacial interactions. In this work, the effects of adding three different commercial coupling agents (NZ12, Lica01, Lica12) to high-density polyethylene (HDPE)/hydroxyapatite (HA) composites were studied. Composites containing 20 parts per hundred (phr) of HA previously treated with the already mentioned coupling agents were characterized by mechanical tests and their morphologies were analyzed afterwards. Composites with 0.3 and 0.5 wt% of NZ12 unfolded an increase in their Young's modulus and tensile strength, as a consequence of an improved dispersion of the filler into the polymeric matrix. Analysis of the samples by XPS showed that the zirconate coupling agent interacted more with the HA, as reflected in the lower binding energies of the corresponding oxygen atoms, which agrees with their better performance from the mechanical point of view.     

Chemically modified nylons as supports for enzyme immobilization

An isocyanide derivative of nylon, polyisonitrile-nylon (1,2), was used as a starting material whereby, through a series of modification reactions, different chemically reactive functional groups could be introduced on the polyamide backbone. The chemistry employed allowed for considerable flexibility in the choice of procedures for covalent fixation of proteins, all starting from the same chemically reactive parent polymer, polyisonitrile-nylon. Thus, polyisonitrilenylon could be used directly for the immobilization of enzymes via fourcomponent condensation reactions. The isocyanide functional groups of the parent polymer could be transformed, by treatment with bromine, into the strongly electrophilic dibromoisocyanide (—N=CBr^b2) groups. The selectivity of the —N=CBr^b2 group toward the various functional groups present in proteins could be regulated by appropriate control of the pH of the coupling reaction. Dibromoisocyanide-nylon was also further modified into other types of chemically reactive nylon derivatives.     

原位沉析法制备可吸收壳聚糖/羟基磷灰石棒材

利用原位沉析法制备出一种以壳聚糖 (Chitosan ,CS)为基体 ,羟基磷灰石 (Hydroxyapatite,HA)为填料的新颖的复合材料 ,系统研究了HA含量对复合材料的力学性能和吸水率的影响 .CS HA的弯曲强度为 6 7 8(MPa) ,弯曲模量为 3 3(GPa) ,剪切强度为 2 1 2 (MPa) ,压缩强度为 4 7 8(MPa) ,均比人的自然骨高 2～ 3倍 ,基本满足了作为骨折内固定材料的力学性能的要求 .HA加入到CS使CS HA复合材料的吸水率下降 ,有助于延缓其力学强度在湿态环境下的衰减     

Towards a model of the mineral-organic interface in bone: NMR of the structure of synthetic glycosaminoglycan- and polyaspartate-calcium phosphate composites

We have synthesised three materials-chondroitin sulphate (ChS, a commercial product derived from shark cartilage and predominantly chondroitin-6-sulphate (Ch-6-S)) bound to pre-formed hydroxyapatite (HA, Ca(10)(PO(4))(6)(OH)(2)), HA formed in the presence of ChS and poly-Asp bound to pre-formed HA-to generate models for the mineral-organic interface in bone. The three materials have been investigated by (13)C cross polarisation magic-angle spinning (CPMAS) NMR, (13)C{(31)P} rotational echo double resonance (REDOR) and powder x-ray diffraction (XRD) in order to verify their composition and to determine the nature of their binding to HA. Our results show that for HA formed in the presence of Ch-6-S, all carbon atoms in the Ch-6-S having contact with mineral phosphate. We propose that HA in this case forms all around the Ch-6-S polymer rather than along one face of it as is more commonly supposed in cases of templating by organic molecules. However, Ch-6-S binding to pre-formed HA probably occurs via a surface layer of water on the mineral rather than to the mineral directly. In contrast, poly-Asp binds closely to the pre-formed HA surface and so is clearly able to displace at least some of the surface-bound water.     

Synthesis of multifunctional Fe3O4 core/hydroxyapatite shell nanocomposites by biomineralization

Superparamagnetic nanoparticles with surface functional groups (-OH, -COOH and -NH(2)) were modified by in situ deposition of hydroxyapatite (HA) on the materials' surface through the biomineralization process to form Fe(3)O(4) core/hydroxyapatite shell nanocomposites. They possess potential applications as targeted carriers for antitumor drugs and as bone tissue engineering scaffolds by integrating multiple functions into a single nanosystem.     

Development of a biologically relevant calcium phosphate substrate for sum frequency generation vibrational spectroscopy

A novel biologically relevant composite substrate has been prepared consisting of a calcium phosphate (CaP) layer formed by magnetron sputter-coating from a hydroxyapatite (HA) target onto a gold-coated silicon substrate. The CaP layer is intended to mimic tooth and bone surfaces and allows polymers used in oral care to be deposited in a procedure analogous to that used for dental surfaces. The polymer cetyl dimethicone copolyol (CDC) was deposited onto the CaP surface of the substrate by Langmuir Blodgett deposition, and the structure of the adsorbed layer was investigated by the surface specific technique of sum frequency generation (SFG) vibrational spectroscopy. The gold sublayer provides enhancement of the SFG signal arising from the polymer but plays no part in the adsorption of the polymer. The surface morphology of the substrate was investigated using SEM and AFM. The surface roughness was commensurate with that of the thermally evaporated gold sublayer and uniform over areas of at least 36 mum(2). The chemical composition of the CaP-coated surface was determined by FTIR and TOF-SIMS. It was concluded that the surface is primarily calcium phosphate present as a mixture of amorphous, non-hydroxylated phases rather than solely stoichiometric hydroxyapatite. The SFG spectra from CDC on CaP were closely similar, both in resonance wavenumbers and in their relative intensities, with spectra of thin films of CDC recorded directly on gold. Application of previous analysis of the spectra of CDC on gold therefore enabled interpretation of the polymer orientation and conformation on the CaP substrate.     

In-Vitro Cytotoxicity Study: Cell Viability and Cell Morphology of Carbon Nanofibrous Scaffold/Hydroxyapatite Nanocomposites

Electrospun carbon nanofibers (CNFs), which were modified with hydroxyapatite, were fabricated to be used as a substrate for bone cell proliferation. The CNFs were derived from electrospun polyacrylonitrile (PAN) nanofibers after two steps of heat treatment: stabilization and carbonization. Carbon nanofibrous (CNF)/hydroxyapatite (HA) nanocomposites were prepared by two different methods; one of them being modification during electrospinning (CNF-8HA) and the second method being hydrothermal modification after carbonization (CNF-8HA; hydrothermally) to be used as a platform for bone tissue engineering. The biological investigations were performed using in-vitro cell counting, WST cell viability and cell morphology after three and seven days. L929 mouse fibroblasts were found to be more viable on the hydrothermally-modified CNF scaffolds than on the unmodified CNF scaffolds. The biological characterizations of the synthesized CNF/HA nanofibrous composites indicated higher capability of bone regeneration.     

Mechanical and dynamic viscoelastic properties of hydroxyapatite reinforced poly(ε-caprolactone)

Poly(ε-caprolactone)/hydroxyapatite (PCL/HA) composites as potential bone substitutes were prepared by melt-blending. The melting, crystallization and glass transition temperatures deduced from differential scanning calorimetery and dynamic mechanical thermal analysis (DMTA) were all changed by the addition of HA, suggesting an interaction at the interface of these two phases. Quasi-static mechanical testing shows that the yield strength and Young's modulus of PCL were increased by the addition of the reinforcement filler, HA. Dynamic viscoelastic properties were investigated using DMTA and an advanced rheometric expansion system. The results show that both the storage modulus and viscous modulus are enhanced by HA, and the PCL composite melts still behave like pseudo-plastic liquid.     

STEM and EDXS characterisation of physico-chemical reactions at the periphery of sol-gel derived Zn-substituted hydroxyapatites during interactions with biological fluids

With its good properties of biocompatibility and bioactivity hydroxyapatite (HA) is highly used as bone substitutes and as coatings on metallic prostheses. In order to improve the bioactive properties of HA, we have elaborated Zn²⁺ doped hydroxyapatite. Zn²⁺ ions substitute for Ca²⁺ cations in the HA structure and four Zn concentrations (Zn/Zn + Ca) were prepared at 0.5, 1, 2 and 5 at.%. To study physico-chemical reactions at the materials periphery, we immersed the bioceramics into biological fluids for intervals from 1 day to 20 days. The surface changes were studied at the nanometer scale by scanning transmission electron microscopy associated with energy dispersive X-ray spectroscopy. After 20 days of immersion, we observed the formation of a calcium–phosphate layer at the periphery of the HA doped with 5% zinc. This layer contains magnesium and its thickness was around 200 nm. Formation of this Ca–P–Mg layer represents the bioactive properties of 5% Zn-substituted hydroxyapatite. This biologically active layer improves the properties of HA and will permit a chemical bond between the ceramic and bone.     

羟基磷灰石在磺化聚醚苯并咪唑薄膜表面的生长

以聚[2,2′-(对氧基联苯)-5,5′-苯并咪唑](OPBI)及其磺化产物磺化聚[2,2′-(对氧基联苯)-5,5′-苯并咪唑](SOPBI)薄膜作为基体, 采用交替沉积和模拟体液(SBF)浸泡相结合的方法快速在薄膜表面沉积羟基磷灰石层. 采用选区电子衍射(SAED)和衰减全反射傅里叶变换红外光谱(ATR-FTIR)对羟基磷灰石(HA)的晶体结构进行了分析. 用扫描电子显微镜(SEM)对整个沉积过程中羟基磷灰石的形态变化进行了跟踪. 实验结果表明, SOPBI薄膜诱导HA沉积的速率明显快于OPBI薄膜. SOPBI的磺酸基团不但提供了固定Ca²⁺的负电表面, 而且还有助于咪唑基团对Ca²⁺的固定. 而缺失磺酸基团的OPBI在不同pH值的交替沉积溶液中的电离形式阻碍了咪唑基团对Ca²⁺和HPO₄^2-的作用, 且未能在SBF浸泡过程中得到改善.     

原位沉析法制备磁性氧化铁羟基磷灰石/壳聚糖棒材

首先通过化学沉淀法制备磁性氧化铁羟基磷灰石(Fe3O4/HA),然后以壳聚糖(CS)为基体,利用原位沉析法将Fe3O4/HA与CS复合,制得磁性Fe3O4/HA/CS复合材料.经XRD、粒径分布和PPMS测试,结果表明了Fe3O4/HA复合物的生成.系统研究了磁性Fe3O4/HA/CS棒材力学性能的影响因素,最终确定Fe3O4与HA质量比为3∶17,磁性Fe3O4/HA与CS质量比为9∶91时,棒材的力学性能最优,弯曲强度可达到87.0 MPa,弯曲模量1.57 GPa.     

Graphene as membrane for encapsulation of yeast cells: protective and electrically conducting

Graphene sheets (chemically reduced), a high modulus and high thermal and electrically conductive material are coupled with yeast cells to form an encapsulating inorganic functional layer. The coupling of the high modulus sheets with the cells increases their stability to osmotic stresses. The sheets also allow the direct visualization of the cells in an electron microscope.     

Preparation and Characterization for the Electrodeposited Hybrid Coating of Calcium Phosphate/Chitosan on Ti Alloy Surface

Hydroxyapatite (HA) formulated as Ca₁₀(PO₄)₆(OH)₂ becomes a favorable material for implants because of its chemical similarity to the calcium phosphate minerals present in biological hard tissue. Many efforts have been made in recent years in the development of processing methods for depositing hydroxyapatite on implant alloy substrate in order to have high strength, good processability, suitable specific density, excellent corrosion resistance in the physiological environment and good affinity to the living body. The plasma spray technique is commonly used in the HA coating on implants. The major problem for the plasma spray, however, is the decomposition and phase transformation of hydroxyapatite during the spray coating process. Electrochemical techniques including electrophretic deposition and electro-deposition are being developed as an alternative method for producing hydroyapatite coated composite material. It is very desirable at present to further strengthen the coating and bond it to the metal substrate, and to increase the bioactivity of hydroxyapatite coatings as well, which is very important for forming a strong chemical bond with natural bone as an implant material.     

Improving mechanical and biological properties of macroporous HA scaffolds through composite coatings

Interconnected porous hydroxyapatite (HA) scaffolds are widely used for bone repair and replacement, owing to their ability to support the adhesion, transfer, proliferation and differentiation of cells. In the present study, the polymer impregnation approach was adopted to produce porous HA scaffolds with three-dimensional (3D) porous structures. These scaffolds have an advantage of highly interconnected porosity (≈85%) but a drawback of poor mechanical strength. Therefore, the as-prepared HA scaffolds were lined with composite polymer coatings in order to improve the mechanical properties and retain its good bioactivity and biocompatibility at the same time. The composite coatings were based on poly(d,l-lactide) (PDLLA) polymer solutions, and contained single component or combination of HA, calcium sulfate (CS) and chondroitin sulfate (ChS) powders. The effects of composite coatings on scaffold porosity, microstructure, mechanical property, in vitro mineralizing behavior, and cell attachment of the resultant scaffolds were investigated. The results showed that the scaffolds with composite coatings resulted in significant improvement in both mechanical and biological properties while retaining the 3D interconnected porous structure. The in vitro mineralizing behaviors were mainly related to the compositions of CS and ChS powders in the composite coatings. Excellent cell attachments were observed on the pure HA scaffold as well as the three types of composite scaffolds. These composite scaffolds with improved mechanical properties and bioactivities are promising bone substitutes in tissue engineering fields.     

Mechanism of activation of hydroxyl-containing polymers with N-hydroxysuccinimide and carbodiimides: Reason for leakage

The carbodiimide-mediated reaction of N-hydroxysuccinimide with carboxyl groups immobilized to hydroxyl-containing polymers (such as Sepharose or Trisacryl) leads to N-hydroxysuccinimide ester and N-hydroxysuccinimide derivatives of β-alanine which react subsequently with the hydroxyl group of the polymer via ester and carbamate bonds. These derivatives are formed upon interaction of dicyclohexyl carbodiimide with three equivalents of N-hydroxysuccinimide followed by a Lossen rearrangement. The amount of β-alanine thus coupled is very high compared to the number of carboxyl groups present on the resin. The β-alanine bound through the ester bond comprises about 90% of the β-alanine bound. Alkaline treatment of the ester bonded β-alanine containing polymers (prior to coupling of amino-containing ligands) causes a rearrangement yielding β-alanine with a free carboxyl group coupled through a stable carbamate linkage. After coupling of amino-containing ligands, the above-described rearrangement cannot occur, and the β-alanine-linked ligand leaks from the polymer via hydrolysis of the ester bond. The newly formed carboxyl groups (derived from the rearrangement) can be used to prepare active esters (e.g. nitrophenyl). Upon coupling with amino-containing ligands, these esters yield resins bearing chemically stable bonds.